Introduction to Purate
Technology & ClO2.
Paul Beattie
February 2016.
Summary
Chlorine dioxide : What is it?
Chlorine dioxide advantages vs other biocides
Chlorine dioxide biofilm removal action
Chlorine dioxide producing methods: pros and cons
SVP Purate technology
Purate: when to consider it
Purate safety
Purate examples
2
Chlorine Dioxide Gas and Disinfectant Characteristics
Greenish-Yellow Color, Similar Smell to Chlorine
Highly Soluble in Water
• Applied as a dissolved gas in water
• Does not hydrolyze like Cl2 : no loss of effectiveness at higher
pHs
• Kills bacteria, spores, viruses, fungi, algae very fast and no
immunity development
• It can diffuse into biofilms attacking the bacteria generating the
biofilm
Reacts by Oxidation (select oxidizer)
• No loss of biocide effectiveness due to byproduct reaction
• No byproduct AOX or THMs
Cannot be compressed or shipped
3
Chlorine Dioxide
Advantages over
other Biocides.
Advantages of ClO2 over Cl2 / Hypo
Very fast rate of disinfection
Excellent control of Bio-films
Effective at low dosage rate
Non Reactive with Organics (No THM or HHA, Low TOX, Low stable consumption)
Non reactive with ammonia (low and stable consumption)
Slow bacterial recovery after disinfection (Chlorite ion)
Disinfection less dependent on pH (stability, economy)
Significantly lower corrosion rate
Safer handling/storing
5
Why Use CIO2 - Selectivity
How chemistry
impacts
dosage
requirements
Amount ‘inactivated’ by
pH effects
Amount available for
disinfection
Amount consumed by
organics
Cl2
ClO2
6
7
Chlorine Dioxide Oxidation Potential.
8
Dosages - Best Practice Guidelines for Recirculating
Cooling Water.
Continuous residual of 0.10 – 0.50 mg/l
• Based on circulation rate (Calculate to 0.10 – 0.20)
• Monitored by ORP
Intermittent slug doses
•
•
•
•
0.10 – 5.0 mg/l residual
(Calculate to 2.00 mg/l) Based on system volume
4-6 times daily
Monitored by ORP (e.g. slug from 200 – 600 mV)
Direct replacement (active:active) of existing oxidizer
• Low demand systems only
• pH dependent
9
How does Chlorine Dioxide Work.
ClO2 disinfects via two separate mechanisms. As a
permeable gas, it migrates through the cell membrane
and reacts selectively with cellular components (amino
acids: cystine, tryptophan and tyrosine) and proteins.
It also inhibits critical cell physiological functions,
including the disruption of protein synthesis via the
oxidation of the disulfide bonds in amino acids and
alteration of the permeability of the outer cell
membrane.
10
Chlorine Dioxide
Biofilm Removal
Action.
The Biofouling Problem
1
2
12
Power Station Treated with
Chlorination
Heat exchanger from a power station treated with chlorine
1
3
13
Power Station Treated with Chlorine
Dioxide
Heat exchanger from a power station treated with chlorine dioxide
1
4
14
The Menace of Bio-films
Because ClO2 is a true dissolved gas in
solution, it can rapidly diffuse and penetrate
the polysaccharide-based biofilm substrate,
killing microbes both throughout and
beneath the biofilm
Reduce heat
transfer in
heat
exchangers
Home for
pathogenes
Cause microbiologicly
induced
corrosion
(MIC, pitting)
Reduce
cooling water
flow
15
Chlorine Dioxide Kill Mechanism.
16
Microbiological Growth & Heat Transfer.
17
Chlorine Dioxide
Generating
Methods Pros &
Cons.
Methods for producing ClO2 – chlorite oxidation

Chlorine + Chlorite
2NaClO2 + Cl2
Advantage
• 100% theoretical chemical
conversion efficiency
• Relatively low cost especially if Cl2 is
locally available
2ClO2 + 2 NaCl
Disadvantage
• Produces THM’s
• Gaseous chlorine is required
• Safety issues for storage.
transportation, and handling
• Higher corrosion (in
recirculating system)
19
Methods for producing ClO2 – chlorite oxidation

ABC method: acid + bleach + chlorite
2NaClO2 + NaOCl + HCl
Advantages
2ClO2 + 3NaCl + H2O
Disadvantages
• 100% theoretical chemical
conversion
• Bleach degradation (especially in
• Elimination of Cl2 Gas
• Three chemical system makes it
more difficult to control & optimize
warm climates)
• High vapor pressure of HCl
20
Methods for producing ClO2 – chlorite oxidation

Chlorite + acid
5NaClO2 + 4HCl
Advantages
• Elimination of Cl2 Gas
• Two component system
• Lowest THM formation of the
chlorite systems
4ClO2 + 5 NaCl + H2O
Disadvantages
• Max 80 % chemical conversion
efficiency
• High vapor pressure of HCl
• Relatively high cost
• Most robust and safe system
of the Chlorite processes
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Methods for producing ClO2 – chlorate reduction

Purate + acid
NaClO3 + ½ H2O2 + ½ H2SO4
Purate ®
ClO2 + ½ Na2SO4 + ½ O2 + H2O
SVP-Pure® Process
Advantages
•
•
•
•
Efficient – 95% conversion at standard conditions
No need of Cl2 Gas
No chloride contribution
High precursor concentration minimize storage
requirements and freight costs
• Converts chlorate directly to ClO2 (not via intermediates as the
Chlorite processes)
•
•
•
•
•
Excellent cost structure
Chlorine Free – no AOX or THM formation
Two Chemical Program – reduces truck traffic
Patented
High quality equipment – safe and reliable
Chemical feed rates per unit mass
of requested ClO2
Purate 78%*
®
H2SO4
4.15
5.16
93%*
H2SO4
98%*
H2SO4
4.33
4.11
* Only one of the acid choices is
needed for SVP-Pure® chemistry.
Acid strengths higher than 78% must
be diluted down before using.
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SP Purate® Technology
Safety is our top priority (audits made for all installations)
Best suited for ClO2 applications greater than 1 kg/h
The State of Art in the Use of Chlorine Dioxide for 23
23
SVP-Pure ® CIO2 Generator Model AD DS
SVP-Pure® ClO2 generator
+ four-point dosing system
24
24
40 Feet ClO2 Production Container
Maximum safety and ease of operation
Fully Enclosed Container (FEC) Inside View
25
Purate : - when to consider it
Large cooling systems with problems
• >2000 l/day bleach
Open recirculating cooling systems
• Minimum recirculation rate 7500 m3/h
Electro-Chlorintors high generating and maintenance costs.
Once through Sea Water Cooling Systems:
• Minimum 20 000m3/h
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Purate Examples.
Sea Water Cooling System.
The Sea Water Cooling System in the Middle East has a history of bio-fouling
leading to poor thermal efficiency and under-deposit corrosion.
Historical attempts to address this had not been successful due to a variety of
factors including efficacy and control problems.
Purate technology has addressed these factors and is providing a significant
improvement in microbiological control and thermal efficiency.
The trial has focused on better targeting of the chlorine dioxide to further
improve cost-effectiveness as we work towards finalizing the target dosage.
Further improvements to safety and monitoring required.
28
29
ClO2 Injection Points & Residuals
Injection point at
traveling screen
(not used)
0.53
0.85
0.55
Injection points
0.35
0.74
1.00
0.49
2.68
0.56
New injection point
(at OHLP Basin)
NB: This does not feed to the
NHLP
Traveling
Screens
ClO2 Residuals
N/A
#
With Old Inj. Points
0.17
#
During High Dose
0.16
#
With New Inj. Points
A recent data point
at Plant #15 inlet
0.07
0.12
0.07
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Heat Exchanger Performance
Total Heat
Transfer
coefficient
(U)
Average 2013
(Feb to 14-Oct)
Average 2014
(7-Feb to 14-Oct)
% Change
Cleanlines
Cooling
s factor
Water Flow
(%)
(m3/h)
145.9
16.9
400.9
176.1
20.5
20.7
20.7
Flow
Velocity
UCleanlines
normalized
s factor
by SW flow normalized
(m/s)
U/SW Flow
Cleanliness
factor/SW Flow
1.6
0.3675
0.0427
454.9
1.8
0.3892
0.0452
13.5
13.5
5.92
5.90
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Plant Data.
31
Visual Inspection
32
Microbiological Analysis
33
Chemical Consumption Results & Target
Last Purate
Consumption
Target
Consumption
based on current
level of monitoring
Feb
Mar
Apr
May
June
July
Aug
Sept
Total
PURATE, Kg 8,562
22,257
19,352
17,845
9,845
11,826
12,611
13,796
116,094
Months
Purate
Winter
2 Pumps
3 Pumps
Summer
2 Pumps
3 Pumps
Taget dosing, ppm
1
1
Running hours, day
4
6
Flow Rate, M3/hr
13,581
20,371
13,581
20,371
Consumption, Kg
Monthly
7,153
10,730
10,730
16,095
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Summary of Improvements
Aspect
Improvement
Safety
A safer system for employees and
environment but more to do
Monitoring & Control
Significant improvements achieved with
additional monitoring (ORP) recommended.
Analysis & Visual
Considerable reductions in microbiological
activity known to contribute to fouling and
under deposition corrosion. Cleaner surfaces.
P15- VDU strainer backwash frequency
improvement
330%
P15 –VDU HX Heat Transfer Coefficient
~ 21/6%
P15- VDU Over-Head Production
~ 7%
MED- Heat Transfer Coefficient
~ 70 %
35
Mussels: Why ClO2?
Sea water flow, 7 000 -10 000 m3/h
Problem with biofilm and mussels
Production losses
Annual cleaning costs in 2010: 2400 k€
High NaOCl dose but little effect
Does not remove the bio-film
AOX and THM problems
Authorities would like them to change
disinfection method
36
Trial follow up – Mussels and bio-film
6 weeks after start up
•Continued to dose hypo during the two first weeks of the trial
•Gradually increased the dose to avoid the bio-film to block the
heat exchangers
•Dosing scheme
•0,2 ppm at the beginning / 0,8 ppm during the summer
•Future expections: 0,2 ppm in winter / 0,5 – 0,6 ppm in
summer
8 weeks after start up
37
K.S.A. Purate Users
Aramco Ras Tanura
Saudi Kayan
Chevron
Safco ( Interested )
Sharq ( Interested )
Tasnee ( Interested )
Ar Razi ( Interested )
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Questions?
39